Sludge centrifuge



Dec. 9, 1969 w. THYLEF'ORS SLUDGE CENTRIFUGE Filed-May 1968 I N VEN TOR. lYEl/lf/C (It 1/564 Tlf" FNPJ' United States Patent U.S. Cl. 233-29 1, Claim ABSTRACT OF DISCLOSURE The separating chamber of the centrifugal rotor contains a set of generally frusto-conical discs including one disc extending radially outside the other discs and dividing them into two separate disc set sections, the second of which (as reckoned in the flow direction through the rotor) has an outlet for separated light liquid and which extends from the inner edges of the discs, this section also having an outlet for separated heavy liquid and which extends from the outer edges of the discs. A passage is provided for flow of liquid from one to the other of the disc set sections, this passage being located at a greater radius than the inner edge of any disc but at a smaller radius than the inlet of the sludge-containing liquid mixture into that part of the separating chamber which contains the first disc set section. The centrifuge is characterized in that the outer edges of the set of discs in the first section are located at a smaller radius than the outer edges of the set of discs in the second section.

The disclosure The present invention relates to centrifugal separators for sludge-containing liquid mixtures. It relates more particularly to such separators of the type in which the centrifugal rotor contains a set of discs arranged in the separating chamber and including one disc which extends radially outside the remaining discs so as' to divide them into two separate disc set sections, the second section of which (as reckoned in the flow direction through the rotor) has an outlet for separated light liquid and which extends from the inner edges of the discs, this second section also having an outlet for separated heavy liquid and which extends form the outer edges of the discs. In this type of centrifuge, the rotor is also provided with a passage for flow of liquid from one to the other of the disc set sections, this passage being situated at a larger radius than the inner edge of any disc but at an appreciably smaller radius than the inlet of the liquid mixture into that part of the separating chamber which contains the first disc set section (as reckoned in the through-flow direction).

A centrifuge of this type is known and is disclosed, for example, in the British Patent 930,159. In such a centrifuge it is possible to separate whey, from which remaining cheese grains as well as cream are separated. According to the present invention, however, it has now been found possible to separate the remaining cream in a more eificient way than in the afore-mentioned prior centrifuge, if the outer edges of said first disc set section are situated at an appreciably smaller radius than the outer edges of said second disc set section. The improved result is obtained with this arrangement due to the fact that it counteracts leakage of whey past the outer edge of the disc which divides the disc set into two sections. The consequence of this is that whey having about the original percentage of cream is prevented from flowing past the outer edge of said dividing disc and the outer edges of the second disc set section and from reaching the outlet for separated heavy liquid without its content of cream having had any opportunity to be separated out. Due to the great radial distance between the outer edge of said dividing disc and the outer edges of the first disc set section in the new centrifuge, the whey passes practically completely inward through the first disc set section and from there through the previously mentioned passage and into the second disc set section, where the remaining content of cream in the Whey is separated out and discharges through the outlet for separated light liquid. i

The invention is described more in detail below with reference to the accompanying drawing, in which the single illustration is a vertical sectional view of the lefthand half of an automatically discharging centrifuge incorporating one embodiment of the invention, although the invention is applicable also to a nozzlecentrifuge or a sludge-accumulating centrifuge.

Referring to the drawing, a rotor body 1 is mounted for rotation about a vertical axis and is provided with a cover 2 and a locking ring 3 for retaining the cover on the body 1. In the wall of the latter are sludge discharge openings 4 adapted to be opened and closed by an axially movable valve disc 5. Liquid to be separated is supplied through a channel 6 in the centrifuge spindle 7 and passes by way of the distributor 8 into the separating chamber 9. In this chamber are two discs set sections 10 and 11 which are separated by a dividing disc 12 having a greater outer diameter than that of the other discs. The discs in the first section 10, situated closer to the inlet 6-8, have a smaller outer diameter than that of the discs in the second section 11. As shown, the discs of both sections, as well as the dividing disc 12, are generally frusto-conical in shape. Like these other discs, the disc 12 has holes 13 for upward through-flow.

Separated light liquid is collected from the two disc set sections 10 and 11 in a central chamber 14 and discharges therefrom through a stationary outlet pipe 15. Separated heavy liquid discharges through a channel 16 and a stationary outlet pipe 17. In the latter pipe is inserted a throttle valve (not shown), by means of which the boundary level between heavy and light liquid can be adjusted to lie somewhere inside the outer edges of the holes 13. The two outlet pipes 15 and 17, which are shown hermetically connected to the rotor top, are sealed against the latter by means of packings 18 and 19. The valve disc 5 is kept in its closing position (pressed against the cover 2) by means of operating liquid (normally water) fed through a stationary channel 20 to an annular chamber 21 in the rotor bottom, from which it passes through a channel 22 into a conical chamber 23 between the underside of the valve disc and the inside of the'rotor body. The operating liquid is supplied at such a flow rate that, despite the outflow through a small draining hole 24, it fills the chamber 23 to a level which is determined by an overflow outlet 25. Excess of operating liquid discharges through this outlet. When the separation chamber of the centrifuge is to be discharged, the supply of the liquid to be separated as well as the supply of operating liquid is interrupted, without the centrifuge being stopped. The liquid in the chamber 23 is then evacuated through the peripheral hole 24, and the valve disc 5 is pressed downward by the rotor content, which then discharges through the openings 4. The valve disc is then returned to its closing position by a new supply of operating liquid, before the separation is resumed.

In the separating operation, the liquid entering the separating chamber 9 passes into the space below the dividing disc 12, where it is freed from the main part of the sludge, the separated sludge forming a cushion 26 at the periphery of the chamber 9. Light liquid separated in this space discharges at the inner edges of the discs 10 to the chamber 14. The heavy liquid is prevented from sliding around the outer edge of the disc 12 but is forced to accompany the unseparated light liquid upwardly into the space above the disc 12 through the holes 13 therein. In the upper disc set section 11, remaining light liquid is separated out and passes inwardly to the chamber 14, and possibly small amounts of sludge pass outwardly to the periphery of the separating space. Clean-separated heavy liquid discharges through the channel 16.

As required, the disc 12 may be placed lower or higher in the stack of discs, thereby adjusting the ratio between the clarifier part and the purifier or concentrator part of the centrifuge to provide the ratio most appropriate for the individual case, so that the centrifuge in its entirety will have as great a throughput capacity as possible.

I claim:

1. A centrifugal separator for a sludge-containing liquid mixture, the separator comprising a rotor mounted for rotation about a central axis and having a separating chamber and an inlet for feeding said mixture to the separating chamber, and a set of generally frusto-conical discs in said chamber including one disc which extends radially outside the other discs and divides said other discs into two separate disc set sections, the first of which sections is located in advance of the second section as reckoned in the direction of liquid flow from said inlet, said second section having an outlet for separated light liquid and which extends from the inner edges of the discs, the second section also having an outlet for separated heavy liquid and which extends from the outer edges of the discs, there being a passage for flow of liquid from one located at a greater radiuc than the inner edge of any to the other of the disc set sections, said passage being disc but at a smaller radius than the opening of said inlet into that part of the separating chamber which contains said first disc set section, the separator being characterized in that the outer edges of the set of discs in said first section are located at a smaller radius than the outer edges of the set of discs in said second section.

References Cited UNITED STATES PATENTS 1,026,271 5/1912 Lesher 23329 2,928,592 3/ 1960 Johnson 23329 X 3,117,928 1/1964 Thylefors 233-29 X WILLIAM I. PRICE, Primary Examiner 2 2-43 UMTED STATES PATENT OFFKCE CERTIFICATE OF CORRECEION Patent No. 3,482,771 Dated Decembft Inventor) Henric Wilhelm Thylefors It is certified that error appears in the aboveddentified patent and that said Letters Patent are hereby corrected as shown below:

Col. 3, line 3, after "prevented", insert ---,by sliding,--.

Co1.- 3, line 4, change "sliding" to --passing--.

Col. 4, line 8, after "one", insert --to the other of the disc set sections, said passage being.

Col. 4, line 9, change "radiuc" to --radius--.

Col. 4, line 10, delete "to the other of the disc set sections, said passage being".

Signed and sealed this 13th day of April 1971 (SEAL) Attest: v

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents 

